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Rising atmospheric CO2 concentrations may lead to hard coral extinction in 100 years

Posted by gmarkets on 17 October, 2007

Berkelmans and Company may be wrong, reported The Sydney Morning Herald (13/10/2007).

Corals may dissolve: Bleaching may not knock off the reef. It may just dissolve first.

Sixty-five million years ago, at the end of the Cretaceous Era, a comet smacked into Mexico’s Yucatan peninsula to unleash the apocalyptic dust cloud that spelled the extinction of dinosaurs. Less famously, the date also marked the disappearance of coral reefs from the fossil record for some two million years, because the released minerals produced so much acid rain that the limestone laid down by corals and shellfish dissolved. (Hence the end of the Cretaceous — the era of chalk.) Today, the ocean chemistry that has allowed coral reefs to flourish was again changing. The same carbon dioxide emissions causing global warming were dissolving into the oceans and mak­ing them more acidic.

Acidification the problem: Brad Opdyke, a geochem­ist with the Australian National University, had been credited as the first to warn, 20 years ago, that acidification would affect coral growth. No one took much notice until around 1998, when Terry Done heard Opdyke speak at a conference. Opdyke had put up a world map showing where corals might survive with predicted changes in ocean chemis­try. There was nowhere. Coming just months after the worst summer of bleaching yet recorded, Done had had his second “Oh f…” moment related to global warming. So far, the ocean’s pH, which was traditionally alkaline, had soured by only 0.1, which of itself was not enough to dissolve limestone. But the growth of reefs was relentlessly trimmed by weathering and by grazing fish, and even modest acidification would slow down growth to tip the balance towards nat­ural erosion.

Possible extinction: Wooldridge, a modeller, and Veron, who had discovered a quarter of Australia’s 400 reef-building coral species, believed if atmospheric carbon dioxide concentrations continued to rise as forecast, the world’s corals would be rendered incapable of net growth in about 50 years. Fifty years after that, all hard coral species would be extinct.